Individual Variation in Glucocorticoid Levels :

.............................................................................................................................. ii Co-Authorship.................................................................................................................... iv Acknowledgements ............................................................................................................. v List of Tables .................................................................................................................... vii List of Figures ................................................................................................................... vii List of Abbreviations ........................................................................................................ vii Chapter 1: General Introduction ......................................................................................... 1 The HPA axis .................................................................................................................. 3 Sources of individual variation in glucocorticoids ......................................................... 4 Repeatability of glucocorticoids ................................................................................... 16 The black-capped chickadee ......................................................................................... 18 Research goal ................................................................................................................ 18 Chapter 2: Circulating glucocorticoids are repeatable in a wild bird during the nonbreeding season ................................................................................................................. 19 Introduction ................................................................................................................... 19 Methods......................................................................................................................... 21 Results ........................................................................................................................... 32 Discussion ..................................................................................................................... 36 Chapter 3: General Discussion .......................................................................................... 43 References ......................................................................................................................... 47 Appendix ........................................................................................................................... 61 Supplementary Fig 1. .................................................................................................... 61 Supplementary Fig 2. .................................................................................................... 62 Supplementary Table 1. ................................................................................................ 63 Supplementary Table 2. ................................................................................................ 64